Method of producing heat transfer plates; an assortment of heat transfer plates; and a plate heat exchanger comprising heat transfer plates included in the assortment

ABSTRACT

In a plate heat exchanger heat transfer plates abut against each other in such a way that heat transfer passages are formed therebetween, port holes provided in the heat transfer plates forming port channels through the plate heat exchanger. Between the heat transfer portion ( 15 ) of a heat transfer plate ( 2 ) and a port hole ( 14 ) forming a part of a port channel, that constitutes an inlet for a refrigerant, the heat transfer plate ( 2 ) has a passage portion ( 16 ). The passage portion ( 16 ) is adapted to delimit a distribution passage between the heat transfer plate ( 2 ) and an adjacent heat transfer plate, through which distribution passage the refrigerant is intended to flow from the inlet port channel to the heat transfer passage between the heat transfer plates. In the distribution passages the refrigerant shall be subjected to a pressure drop. According to the invention the pressure drop can be given different magnitudes by punching of different kinds of port holes ( 14 ) in the heat transfer plates.

FIELD OF THE INVENTION

The present invention concerns a method of producing heat transferplates, which are of the same size and have central heat transferportions of the same shape. Each of the heat transfer plates has onrespective sides of the heat transfer portion through holes, so calledport holes, for through flow of at least one heat exchange fluid.Additionally each heat transfer plate has a passage portion which, whenthe heat transfer plate abuts against another heat transfer plate in aplate heat exchanger, is adapted to delimit a distribution passage forthrough flow of said heat exchange fluid. The passage portion extendsfrom one of said port holes to an area in or near said heat transferportion, which area has the same position in relation to the heattransfer portion in the different heat transfer plates. Duringproduction of the heat transfer plates separate operations are carriedout for pressing the passage portions of the heat transfer plates andfor punching the holes which shall form said port holes, respectively.

BACKGROUND OF THE INVENTION

In a plate heat exchanger heat transfer plates abut against each otherin a way such that they form a plate package with heat transfer passagesbetween the heat transfer plates. The port holes of the heat transferplates form port channels through the plate package.

Plate heat exchangers are often used as evaporators in cooling systems.In such a plate heat exchanger most often at least one heat exchangefluid, which is constituted by a refrigerant, flows into one of the portchannels in the form of a liquid-gas mixture. From the port channel therefrigerant is conducted through inlet or distribution passages, of thekind initially mentioned, into the heat transfer passages intended forthe refrigerant. When flowing through the distribution passages therefrigerant is subjected to a substantial pressure drop, whereby asnearly even a distribution of the refrigerant between the different heattransfer passages as possible is achieved. In the heat transfer passagesthe refrigerant evaporates by absorbing heat from another heat exchangefluid flowing through adjacent heat transfer passages.

In the past only a few rather similar refrigerants have been used inmost cooling systems. Plate heat exchangers for such cooling systemshave been produced in several different sizes, but plate heat exchangersof the same size have normally been given a uniform design, irrespectiveof the refrigerant to be used in them. Thus, the distribution passageshave had the same dimensions in all plate heat exchangers of a specificsize, which has meant that the pressure drop to which a refrigerant hasbeen subjected in the distribution passages has not necessarily beenoptimal for this particular refrigerant.

As a consequence of old environmentally dangerous refrigerants, havingbeen forbidden and a large number of new more environmentally friendlyrefrigerants having been introduced, a need has arisen for adaptation ofthe pressure drop in the distribution passages individually for eachplate heat exchanger with regard to the refrigerant to be used in it.The new refrigerants, in other words, show large individual differencesbetween their evaporation pressures at a specific temperature.

SE 8702608-4 shows a plate heat exchanger formed with restrictions,which are adapted to reduce the pressure of a refrigerant, when it flowsfrom a port channel into a number of heat transfer passages. Therestrictions can be constituted by holes drilled in rings, which arearranged between the heat transfer plates around the port channel, or byholes drilled in a pipe, which is arranged in the port channelconstituting the inlet channel for the refrigerant. According to afurther embodiment the heat transfer plates may abut against each othertwo by two around the port holes forming the inlet channel for therefrigerant, except in limited areas where inlet passages have beenleft. The restrictions can be adapted to a certain refrigerant, acertain pressure drop and a certain temperature difference.

SUMMARY OF THE INVENTION

The object of the present invention is to produce, in a simple and costeffective way, heat transfer plates of the initially described kind,which are intended for plate heat exchangers of different kinds withrespect to the pressure drop that is to be attained in theirdistribution passages.

This object can be achieved, by means of the initially mentioned methodof producing heat transfer plates, by providing by said punchingoperation each one of separate or interconnected sheet metal pieces,which are to form the said heat transfer plates, with holes in a waysuch that the one port hole in a first sheet metal piece is of adifferent kind than the corresponding port hole in a second sheet metalpiece, the respective port holes of the sheet metal pieces being shapedby the punching operation such that they result in finished heattransfer plates having differently sized passage portions.

By the invention heat transfer plates for plate heat exchangers, whichare individually adapted for different refrigerants, can be produced atalmost the same cost as heat transfer plates for plate heat exchangers,which are not individually adapted for different refrigerants. Theinvention contemplates that different punching tools are used for thepunching of port holes of different kinds. However, the increase in costfor each heat transfer plate, as a consequence of this, will be marginalin connection with a large production series.

Either the punching operation for punching said port hole can beperformed before the pressing operation for the shaping of the passageportions, or the two operations can be performed in the inverse order.

The port holes of different kinds can be shaped as circles but withdifferent diameters; alternatively they can be given a shape differingfrom a circular shape. In these different ways the heat transfer platescan easily be provided with differently sized passage portions.

Normally the heat transfer portion of a heat transfer plate is providedwith a pressing pattern of depressions and elevations by a pressingoperation. It is convenient to shape the passage portion of the heattransfer plate in the same pressing operation.

In a preferred way of carrying out the method according to the inventionthe passage portion of each of the heat transfer plates is shaped sothat it forms a groove. Thus, a distribution passage between twoadjacent plates in a plate heat exchanger will be given the shape of achannel having a specific uniform through flow area. It is easy tocalculate which length such a channel should have for obtaining of thedesired pressure drop in a refrigerant flowing through the channel.

The passage portion can alternatively be provided with a pressingpattern of elevations and/or depressions.

The invention also concerns an assortment of heat transfer plates, whichare of the same size and have central heat transfer portions of the sameshape. Each of the heat transfer plates has through holes, so calledport holes, on the respective sides of its heat transfer portion forthrough flow of at least one heat exchange fluid and one passage portionwhich, when the heat transfer plate abuts against another heat transferplate in a plate heat exchanger, is adapted to delimit a distributionpassage for through flow of the heat exchange fluid. The passage portionextends from one of the port holes to an area in or near the heattransfer portion, which area has the same position in relation to theheat transfer portion in each of the different heat transfer plates.

The heat transfer plates of the assortment are characterized in thattheir port holes at the respective passage portions are of differentkinds and shaped such that the passage portions of the heat transferplates have different sizes.

The phrase an assortment of heat transfer plates, when used here, shouldbe understood to mean at least two different kinds of heat transferplates. In a plate heat exchanger comprising heat transfer plates fromthe assortment according to the invention, either heat transfer platesof one kind or heat transfer plates of two or several kinds can beincluded. The latter alternative can be suitable if the plate package ofthe plate heat exchanger comprises many heat transfer plates and, thus,long port channels. In such long port channels the heat exchange fluidsare subjected to pressure drop. In order to obtain in this case an equaldistribution of the refrigerant between the heat transfer passages thedistribution passages, thus, may have to be differently sized along theport channel forming an inlet of the plate heat exchanger.

Finally, the invention also concerns a plate heat exchanger comprisingheat transfer plates of at least one kind included in the abovediscussed assortment. A plate heat exchanger of this kind ischaracterized in that the relationship between the smallest through flowarea of a distribution passage and the through flow area of port hole isbetween 0.0002 and 0.05, preferably between 0.0007 and 0.017. Theserelationships as a rule are relevant for plate heat exchangers used asevaporators in cooling systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described more closely with reference to theaccompanying drawings, in which FIG. 1 shows a brazed plate heatexchanger and FIG. 2 shows a section along the line II—II through thebrazed plate heat exchanger in FIG. 1. FIGS. 3, 5, 7 and 8 show cornersof heat transfer plates having port portions according to differentembodiments of the invention. Only the port portions of the heattransfer plates are correctly presented with respect to their functionin FIGS. 3, 5, 7 and 8, whereas the remaining plate portions are onlyschematically shown. FIGS. 4 and 6 show sections through the heattransfer plates of FIGS. 3 and 5, respectively.

DETAILED DESCRIPTION

FIG. 1 shows a plate heat exchanger 1 designed to be used as anevaporator in a cooling system. The plate heat exchanger 1 comprisesheat transfer plates 2, which are provided with pressing patterns ofelevations and depressions and are brazed together to form a platepackage. The heat transfer plates 2 abut against each other such that afirst and a second set of heat transfer passages are formed between theheat transfer plates 2 for through flow of two heat exchange fluids.Onto each one of the two outer heat transfer plates of the plate packagean end plate is brazed. One such end plate 3 is provided with fourconnection pipes 4-7.

Every heat transfer plate 2 is provided with four port holes, each inline with one of the connection pipes 4-7, respectively. The port holesin the heat transfer plates 2 form four port channels through the platepackage. Two of the port channels, aligned with the connection pipes 4and 5, communicate with the first set of heat transfer passages and theother two port channels, which are aligned with the connection pipes 6and 7, respectively, communicate with the second set of heat transferpassages. One of the heat exchange fluids is constituted by arefrigerant, which is intended to flow through the first set of heattransfer passages of the heat exchanger from the connection pipe 4 tothe connection pipe 5. Consequently, the second heat exchange fluid isintended to flow through the second set of heat transfer passages of theplate heat exchanger 1, suitably from the connection pipe 6 to theconnection pipe 7.

FIG. 2 shows a section through a plate heat exchanger 1 along the lineII—II in FIG. 1. The heat transfer plates 2 abut against each other inpairs around two 8, 9 of their port holes, forming two port channels 10and 11, respectively, and delimiting said first and second sets of heattransfer passages 12, 13. The port channel 10 and the connection pipe 5form an outlet for the said refrigerant and are connected with the firstset of heat transfer passages 12. The connection pipe 6 and the portchannel 11 form an inlet for the second heat exchange fluid and areconnected with the second set of heat transfer passages 13.

FIG. 3 shows a corner portion of a heat transfer plate 2 according to apreferred embodiment of the invention. In the corner portion the heattransfer plate 2 is provided with a port hole 14 which is aligned withthe connection pipe 4 in FIG. 1. When several heat transfer plates 2abut against each other in a plate package, the port holes 14 of theheat transfer plates 2 form the port channel which together with theconnection pipe 4 form the inlet for the refrigerant into the plate heatexchanger. Between the port hole 14 in each heat transfer plate 2 and aheat transfer portion 15 thereof there is a passage portion in the formof a pressed groove 16.

FIG. 4 shows a section through four heat transfer plates 2 along theline IV—IV in FIG. 3. The heat transfer plates 2 abut in pairs againsteach other around the port holes 14, the pressed grooves 16 of the heattransfer plates of each such pair forming a distribution passage in theshape of a channel 17. The port holes 14 form together a port channel18. By punching differently sized port holes 14 in the heat transferplates 2, for example along any of the lines 19, 20 in FIG. 3, differentlengths for the distribution passage, i.e. the channel 17, can beaccomplished.

When the refrigerant flows via the channels 17 from the port channel 18into the heat transfer passages 12 formed between the heat transferportions 15 of the heat transfer plates 2, the refrigerant is subjectedto a pressure drop which is dependent on the length of the channels 17.By adaptation of the length of the channels 17 a desired pressure dropand, thus, an optimal evaporation of a specific refrigerant can beobtained.

FIG. 5 shows the corner portion of a heat transfer plate 2 according toanother embodiment of the invention. The heat transfer plate 2 has aport hole 21, which together with corresponding port holes in other heattransfer plates 2 in a plate heat exchanger, wherein it is included,form the inlet channel of the refrigerant. According to this embodimentof the invention a passage portion 22 of the heat transfer plate 2 bypressing has been provided with a pattern of elevations and depressions23. Dotted lines 24, 25 mark punching lines along which the port holecan be punched and thus be given different diameters.

FIG. 6 shows a section through four heat transfer plates 2 along theline VI—VI in FIG. 5. However, only every second heat transfer plate 2is provided with elevations and depressions 23 in its passage portion.The heat transfer plates 2 abut tightly against each other in pairsaround the ports 21 except near the passage portions, where the abutmentbetween the heat transfer plates 2 is such that a distribution passage26 is formed between the heat transfer plates 2. The length of thedistribution passage 26 can be shortened by enlargement of the diameterof the port hole 21.

A further embodiment of the invention is shown in FIG. 7. The areaaround the port hole 27 of a heat transfer plate 2 is here provided witha passage portion, in which a helically shaped groove 28 is pressed.Also in this embodiment the length of the groove 28 can be reduced byenlargement of the diameter of the port hole 27.

FIG. 8 shows a corner portion of a heat transfer plate 2 according toyet another embodiment of the invention. The passage portion between aport hole 29 and the heat transfer portion 15 of the heat transfer plate2 is provided with three pressed grooves 30, 31, 32 of differentlengths. When the heat transfer plate 2, around the port hole 29, abutsagainst another heat transfer plate, which has a port hole of the samesize, only the groove 30 will form a channel between the edge of theport hole 29 and the heat transfer portion 15. Upon punching out a partof the heat transfer plate 2 along lines 33 and 34, respectively, alsothe groove 31 and the grooves 31 and 32, respectively, will formchannels between the edge of the port hole and the heat transfer portion15. The more open channels are created the less pressure drop therefrigerant will be subjected to when it flows from the port hole to theheat transfer portion 15.

Many more embodiments of the invention are possible. E.g. all the heattransfer plates 2 shown in FIG. 6 could be provided with elevations anddepressions 23 in their passage portions 22, and in the embodiment shownin FIG. 4 only every second heat transfer plate 2 would need to beprovided with a pressed groove 16. In the embodiments according to FIG.3 and 4, and FIG. 5 and 6, the length of the channel 17 and thedistribution passage 26, respectively, could be changed by punching outa part of the heat transfer plates 2 in the way shown by the lines 33and 34 in FIG. 8, instead of by enlargement of the diameter of the portholes 14 and 21, respectively. The plate heat exchanger 1 shown in FIG.1 could be designed for so called diagonal flow, i.e. the refrigerantwould be intended to flow through the plate heat exchanger 1 from theconnection pipe 4 to the connection pipe 6, and the other heat exchangefluid would be intended to flow through the plate heat exchanger betweenthe connection pipes 5 and 7.

It has been suggested above that different kinds of port holes should beshaped in heat transfer plates, the passage portions of which areprovided with grooves or other irregularities, for achievement ofdistribution passages giving different through flow resistance. Withinthe scope of the invention it is possible, however, to achieve this byinstead shaping different kinds of port holes, e.g. port holes ofdifferent sizes or different shapes, in heat transfer plates havingcompletely smooth passage portions. Thus, for example the plates 2 shownin FIG. 6, which have no elevations or depressions 23 in their passageportions, may be provided with larger port holes than the plates 2,which have such elevations and depressions 23. Also in this way thedistribution passages in question can be given a smaller through flowresistance than they have with the shape of the port holes in the heattransfer plates as shown in FIG. 6. In other words, if two adjacent heattransfer plates are of different kinds with respect to the design oftheir passage portions, as in FIG. 6, the through flow resistance, whichis given by the distribution passage formed between the heat transferplates, can be changed by either one or the other—or both—of the heattransfer plates being provided with larger port holes or port holes of adifferent kind.

The heat transfer plates 2 according to the invention can be producedfrom either separate or interconnected sheet metal pieces. In everysheet metal piece first the port hole 14; 21; 27; 29, which is to formpart of the inlet channel of the refrigerant, can be punched and,thereafter, the passage portion can be pressed. Suitably all port holesin every sheet metal piece are punched in the same punching operationand, suitably, the passage portion is shaped in the same pressingoperation as the one during which the sheet metal piece is provided witha pressing pattern in its heat transfer portion 15. The punching andpressing operations can be performed in either one or the other order,as mentioned earlier.

What is claimed is:
 1. A method of producing heat transfer plates (2),which are of the same size and have central heat transfer portions (15)of the same shape, each of the heat transfer plates (2) having throughholes, so called port holes (8, 9; 14; 21; 27; 29), on respective sidesof its heat transfer portion (15) for through flow of at least one heatexchange fluid and one passage portion (16; 22; 28; 30, 31, 32) which,when the heat transfer plate (2) abuts against another heat transferplate in a plate heat exchanger, is adapted to delimit a distributionpassage (17; 26) for through flow of said heat exchange fluid and whichextends from one (14; 21; 27; 29) of said port holes to an area in ornear said heat transfer portion (15), which area has the same positionin relation to the heat transfer portion (15) in each of the heattransfer plates (2), separate operations being carried out for pressingthe passage portions (16; 22; 28; 30, 31, 32) of said heat transferplates (2) and for punching the holes which shall form said port holes(8, 9; 14; 21; 27; 29), respectively, comprising providing by saidpunching operation each one of separate or interconnected sheet metalpieces, which are to form the said heat transfer plates (2), with holesin a way such that said one port hole (14; 21; 27; 29) in a first sheetmetal piece becomes of a different kind than the corresponding one porthole (14; 21; 27; 29) in a second sheet metal piece, the said one portholes (14; 21; 27; 29) of the sheet metal pieces being shaped by thepunching operation such that they result in finished heat transferplates (2) having differently sized passage portions (16; 22; 28; 30,31, 32).
 2. A method according to claim 1, in which each sheet metalpiece is first subjected to the punching operation for punching said oneport hole (14; 21; 27; 29) and thereafter subjected to the pressingoperation for shaping the said passage portion (16; 22; 28; 30, 31, 32).3. A method according to claim 1, in which each sheet metal piece isfirst subjected to the pressing operation for shaping the said passageportion (16; 22; 28; 30, 31, 32) and thereafter subjected to thepunching operation for punching said one port hole (14; 21; 27; 29). 4.A method according to claim 1, in which the said one port holes (14; 21;27) of different kinds are shaped circular but with different diameters.5. A method according to claims 1, in which at least one of said oneport holes (29, 33, 34) is given a shape differing from circular shape.6. A method according to claim 1, in which the pressing operation forthe shaping of the said passage portion (16; 22; 28; 30, 31, 32) of eachof the heat transfer plates (2) is carried out at the same time as theheat transfer portion (15) of this heat transfer plate (2) is providedwith a pressing pattern of depressions and elevations.
 7. A methodaccording to claim 1, in which the said passage portion of each of theheat transfer plates (2) is shaped so that it forms a groove (16; 28).8. A method according to claim 1, in which the said passage portion (22)of each of the heat transfer plates (2) is provided with a pressingpattern of elevations and/or depressions (23).
 9. An assortment of heattransfer plates (2), which are of the same size and have central heattransfer portions (15) of the same shape, each of the heat transferplates (2) having through holes, so called port holes (8, 9; 14; 21; 27;29), on respective sides of its heat transfer portion (15) for throughflow of at least one heat exchange fluid and one passage portion (16;22; 28; 30, 31, 32) which, when the heat transfer plate (2) abutsagainst another heat transfer plate in a plate heat exchanger, isadapted to delimit a distribution passage (17; 26) for through flow ofsaid heat exchange fluid and which extends from one (14; 21; 27; 29) ofsaid port holes to an area in or near said heat transfer portion (15),which area has the same position in relation to the heat transferportion (15) in each of the different heat transfer plates, wherein thesaid one port holes (14; 21; 27; 29) of the heat transfer plates (2) atthe respective said passage portions (16; 22; 28; 30, 31, 32) are ofdifferent kinds and are shaped such that the passage portions (16; 22;28; 30, 31, 32) of the heat transfer plates (2) have different sizes.10. An assortment of heat transfer plates according to claim 9, in whichthe said passage portions (16; 28; 30, 31, 32) of the respective heattransfer plates (2) form grooves (16; 28; 30, 31, 32) having differentlengths.
 11. An assortment of heat transfer plates (2) according toclaim 9, in which the said passage portions (22) of the respective heattransfer plates (2) are provided with pressing patterns of elevationsand/or depressions (23).
 12. An assortment of heat transfer plates (2)according to claim 9, in which the said one port holes (14; 21; 27) ofdifferent kinds are circular but have different diameters.
 13. Anassortment of heat transfer plates (2) according to the claim 9, inwhich at least one of said one port holes (29, 33, 34) of differentkinds has a shape differing from circular shape.
 14. A plate heatexchanger comprising heat transfer plates (2) of at least one kind beingincluded in an assortment according to any one of the claims 9-13, eachof said heat transfer plates (2) having a central heat transfer portion(15), through holes, so called port holes (8, 9; 14; 21; 27; 29), onrespective sides of its heat transfer portion (15) for through flow ofat least one heat exchange fluid and a passage portion (16; 22; 28; 30;31; 32), which is adapted to delimit a distribution passage (17; 26)between two adjacent heat transfer plates (2) in a plate heat exchangerfor through flow of said heat exchange fluid and which extends from one(14; 21; 27; 29) of said port holes to an area in or near said heattransfer portion (15), which area has the same position in relation tothe heat transfer portion (15), in the different heat transfer plates(2), wherein the relationship between the smallest through flow area ofsaid distribution passage (17; 26) and the through flow area of said oneport hole (14; 21; 27; 29) is between 0.0002 and 0.05.
 15. A plate heatexchanger according to claim 14, wherein the relationship between thesmallest through flow area of said distribution passage (17; 26) and thethrough flow area of said one port hole (14; 21; 27; 29) is between0.0007 and 0.017.